Intermittent fasting for rapid weight loss may increase diabetes risk

Naveed Saleh, MD, MS, for MDLinx | August 29, 2018

Intermittent fasting interferes with insulin activity and might heighten diabetes risk, according to study findings presented at the European Society of Endocrinology 2018 annual meeting hosted in Barcelona, Spain.

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The main effect of intermittent fasting in rats was impairment of insulin secretion, which reduced weight but also significantly increased adipose tissue and stomach size (control rat on left, treated rat on right). (Images: University of Sao Paulo)

“This is the first study to show that, despite weight loss, intermittent fasting diets may actually damage the pancreas and affect insulin function in normal healthy individuals, which could lead to diabetes and serious health issues,” stated investigator Ana Bonassa, PhD candidate in biology, University of Sao Paulo, Brazil.

Intermittent fasting diets have garnered much attention recently. Studies examining the efficacy of such diets, however, have yielded mixed results, and some experts question the long-term effects of this dietary approach. Furthermore, previous research has shown that intermittent fasting can produce free radicals. More generally, fasting leads to physiological changes in the pancreas: altering insulin secretion, pancreatic islet metabolism, and the redox state of pancreatic beta cells.

In the current study, investigators analyzed whether fasting every other day affected body weight, food intake, free radical levels, and insulin function in rat models. After 3 months of intermittent fasting, the team then sacrificed the rats to assess pancreatic islets, perigonadal white adipose tissue, extensor digitorum longus muscle tissue, and liver samples.

The investigators found that intermittent fasting did reduce body weight and food intake in rats, but also markedly increased the size of the stomach. The amount of adipose tissue increased, whereas the amount of muscle tissue decreased. Plasma insulin levels increased at both baseline and following glucose administration.

In vitro, intermittent fasting heightened insulin secretion, glucose metabolism, and net reactive oxygen species production in pancreatic islets, as well as reducing the mass of these islets. Furthermore, AKT phosphorylation was impaired in peripheral tissues, indicating insulin resistance.

The team noted that intermittent fasting in rats had negative repercussions on tissue homeostasis, even though weight loss occurred. Intermittent fasting resulted in both in vivo and in vitro hyperinsulinemia and peripheral insulin resistance, along with increased insulin secretion by pancreatic islet cells. Finally, decreased pancreatic islet cell mass after 3 months of intermittent fasting likely compromised glucose balance.

“We should consider that overweight or obese people who opt for intermittent fasting diets may already have insulin resistance,” Bonassa reflected, “so although this diet may lead to early, rapid weight loss, in the long-term there could be potentially serious damaging effects to their health, such as the development of type 2 diabetes.”

Further studies are needed to corroborate the effects in humans, the researchers noted.

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